During manufacturing process for the liquid crystal substrate, to enable the liquid crystal molecules to form a certain pretilt angle, there is a need to perform rubbing alignment for the alignment film on the substrate.
As the size of the liquid crystal substrate becomes larger, the size of the motherboard used in the rubbing alignment process also increases, but the utilization rate of the motherboard is reduced. The motherboard is usually divided into multiple substrates. The region where the substrate resides is an effective region of the motherboard, which is to be manufactured into a liquid crystal substrate, while the region between adjacent substrates is an ineffective region of the motherboard, which is to be discarded after cell alignment and cutting. The proportion of the area of the effective regions in the total area of the motherboard is the utilization rate of the motherboard. For example, in case the size of a motherboard is 2200 mm×2500 mm, the utilization rate thereof is 75% when it is cut into 43-inch substrates, and the utilization rate thereof is 84.95% when it is cut into 46-inch substrates. In order to increase the utilization rate of the motherboard, it is possible to generate substrates having different sizes from one and the same motherboard. For example, when substrates having sizes of 43 inches and 18.5 inches are generated simultaneously from one motherboard, the utilization rate of the motherboard is 90.3%.
However, the existing rubbing alignment device is only applicable to rubbing for a motherboard which is divided into a plurality of identical substrates arranged uniformly. If different substrates of one and the same motherboard are rubbed, the difference between different substrates would affect the uniformity in rubbing alignment, thereby affecting the liquid crystal alignment, resulting in an abnormality in the displayed image.
FIGS. 1 and 2 are schematic views showing existing rubbing alignment for a substrate. As shown in FIG. 1 or 2, a friction roller 11 ascends or descends in the direction of the arrow under the effect of an elevator (not shown). Since there is a significant difference in the thickness between the effective region and the ineffective region of the motherboard, an imprint 12 that coincides with the boundary between the effective region and the ineffective region would be formed on the friction cloth of the friction roller during rubbing alignment. However, referring to FIG. 2, in case the distribution of the effective regions and the ineffective regions in a rear section of the motherboard is different from that in a front section of the motherboard, or multiple substrates of different sizes are distributed on one and the same motherboard, such friction cloth with imprint will leave an imprint in the effective region during rubbing alignment for the rear section of the motherboard, thus affecting the quality of the liquid crystal panel, resulting in poor or abnormal display. Therefore, when the existing rubbing alignment device performs rubbing for a motherboard divided into multiple different substrates, the uniformity in rubbing alignment would be affected, which in turn would have a great influence on the uniformity of the liquid crystal alignment, resulting in poor panel quality, etc.